The present invention relates to apparatus for exposing a plurality of articles to a gaseous or vaporous medium in a successive manner.
A known apparatus for exposing a continuous supply of articles to a gaseous or vaporous medium for instance machines for drying articles such as printed material, have often consisted of a long, substantially horizontal, conveyor belt on which articles to be dried are placed. The articles are conveyed along the belt to a drying station at which they are dried as they pass through.
A disadvantage of this type of machine is that, since they are longitudinally orientated they require a great deal of floor space the belt being necessarily of extended length.
Alternatively, it is often customary to dry articles at the drying station by placing them on drying racks, where the articles dry at ambient temperature by evaporation. The racks may comprise a frame having a series of wire mesh trays which are orientated horizontally whilst articles are loaded on to them, the trays having been lowered sequentially from an inclined position to accept the work. A disadvantage of these trays is that sufficient time must elapse for the last article to dry before the trays can be cleared, thus necessitating the use of at least two drying racks at the same time.
Further existing types of drier include the vertical tower dryer and the so-called wicket dryer. The vertical tower dryer comprises a system of trays supplied to a housing arranged to accommodate a column of trays carried upwardly through a heating zone, each tray as it reaches the top of the column being transferred horizontally to a cooling section of the housing, through which it then descends in a second column before delivery to a stacking device. These machines, although taking up comparative little floor space, are very tall, and require adequate roof height.
A wicket dryer is a machine having a horizontal layout, comprising a conveyor belt with slanting projections or flights, each arranged to support a sheet at an inclined angle as the upper, operative rum of the conveyor passes through the heating zone. As each flight passes over the end of the conveyor to commence a lower return run, the articles may be removed if required, or they may be retained in place and returned to a stacking device adjacent the commencement of the operative run, if preferred. In any case, this machine takes up a great deal of factory floor space.